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Re: [Amps] conversion scale from dbu to microvolts

To: "Fern Rivard" <crc@cyberlink.bc.ca>, <amps@contesting.com>
Subject: Re: [Amps] conversion scale from dbu to microvolts
From: Karl-Arne Markström <sm0aom@telia.com>
Reply-to: Karl-Arne Markström <sm0aom@telia.com>
Date: Sat, 29 Jul 2006 16:12:01 +0200
List-post: <mailto:amps@contesting.com>
dBu is a measure of voltage, expressed as dB relative to 1 microvolt.

There is one major problem with this expression, as it also has to be referred 
to the termination. 

It can be either "dBu EMF" which is the preferred way of expressing receiver 
sensitivities in terms of the generator
EMF before its output impedance, or "dBu pd" which is the actual potential 
difference over the receiver input.

They differ by a factor 2 or 6 dB.

If "dBu EMF" is assumed, 

- 7 dBu corresponds to 0,44 uV EMF or -120 dBm
- 13 dBu corresponds to 0,22 uV EMF or -126 dBm
+20 dBu corresponds to 10 uV EMF or - 93 dBm


73/

Karl-Arne
SM0AOM


----- Original Message ----- 
From: "Fern Rivard" <crc@cyberlink.bc.ca>
To: <amps@contesting.com>
Sent: Saturday, July 29, 2006 3:06 PM
Subject: [Amps] conversion scale from dbu to microvolts


> 
> 
> 
> >    I just received the service manual for my Yaesu FT-1500M and would 
> > like to calibrate the S-Meter but unfortunately Yaesu uses dbu's which 
> > is all dutch to me as all of my test gear use either microvolts or 
> > dbm.
> >    It would be nice to find a conversion scale for this but Google did 
> > not bring up a chart for me.  For now, I need the conversion into 
> > either microvolts or dbm of:
> >
> > 1)   -7dbu
> >
> > 2) -13 dbu
> >
> > 3) + 20 dbu
> >
> >    Thanks from Fern
> >
> > 
> 
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